1. Field of the Invention
The present invention is broadly concerned with a method and apparatus for the preparation of pelletized modified sulfur concrete which can be shipped and stored for indefinite periods and simply remelted at a construction site so as to provide a coherent pourable mass of modified sulfur concrete. More particularly, it is concerned with such a method and apparatus (and the resultant pelletized product) which are characterized by treatment of hot modified sulfur concrete in an elongated auger-type mixing chamber along with injected pressurized air and water to solidify and freeze the concrete in a pelletized, remeltable form.
2. Description of the Prior Art
U.S. Pat. No. 4,348,313 describes an improved modified sulfur concrete preferably comprising aggregate, mineral filler and sulfur cement, the latter being composed of 95% sulfur and 5% plasticizer. The plasticizer in turn comprises a 50%--50% blend of dicyclopentadiene and oligomers of cyclopentadiene. Such improved concrete is formed by initially heating the aggregate (e.g., rock and sand) to approximately 375.degree. F. in a rotary dryer, whereupon the heated aggregate is transferred into a mixing truck heated by catalytic heaters. The modified sulfur cement is then added to the aggregate along with the mineral filler, typically fly ash. Such additions bring the temperature of the total mixture down to about 270.degree. F., and mixing proceeds at or above this temperature until a homogeneous concrete mixture is obtained. The modified sulfur concrete can then be poured in the conventional manner.
Modified sulfur cement produced in accordance with U.S. Pat. No. 4,348,313 has proven to be extremely resistent to most mineral acids and salts and develops high early strength because of its rapid set upon cooling. In addition, the finished concrete product exhibits enhanced freeze-thaw stability and strength characteristics.
Modified sulfur concrete of the type in question is further described in a brochure distributed by National Chempruf Concrete, Inc. of Clarksville, Tenn. entitled "Modified Sulfur Concrete Is The Construction Alternative In Highly Corrosive Environments"; this brochure, together with U.S. Pat. No. 4,348,313, are incorporated by reference herein.
While modified sulfur concrete of the type described has achieved widespread use, problems remain insofar as the handling and formulation thereof are concerned. For example, in many instances it would be desirable to premix the concrete ingredients at ambient temperature, and ship these to a construction site for heating and use. However, attempts along these lines have proved unworkable in that the materials tend to absorb moisture and/or separate out over time, producing nonhomogeneous compositions. As a consequence, it is heretofore been necessary to separately provide the starting materials and mix and heat these on site to provide a finished concrete product.